Direct trip device



Jan. 7, 1936. M A BOSTWICK 2,027,221

DIRECT TRIP DEVICE Filed July 19, 1934 3 Sheets-Sheet 1 .Za @M Jan. 7,1,936. M. A. Bos'rwlcK DIREG'I1 TRIP DEVICE 5 Sheets-Sheet 2 Filed July19", 1934 P/a/Vea/ Sepa/wien INVENTOR /Vyrofz A. Eosfzaz'c/.

swf. ATT NEY Jal-1. 7, 1936. M A BOS-[WICK 2,027,221

DIRECT TRIP DEVICE Filed July 19, 1934 3 Sheets-Sheet 5 umm Ill

WITNESSEYS: INVENTOR ritmica .im 7, 193e UNITEDA rrxrEs'` PATENT OFFICEDIRECT 'nur DEVICE lMyron a'mtwick, Spokane, Wash., miglior toWestinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application July 19, 1934, Serial No.736,022

14 Claims.

y 5 particularlyA applicable to network protectors.

Various direct-trip devices having power-directional characteristicshave heretofore been proposed, but, so far as I am aware, all suchdevices of the prior art have either had undesirable charlo acteristics,such as a circular tripping curve, or

have been unable to deliver a powerful mechanical tripping impulseunless built to an undesirably large scale.

It is'accordingly an object of my invention to l5 provide a noveldirect-trip device which shall have substantially straight-line or otherdesirable tripping characteristics, and which shall operate to deliver apowerful mechanical tripping. impulse for'a given size or weight of thedevice.

20 Other objects oi' my invention will become evident from the followingdetailed description, taken in conjunction with the accompanyingdrawings, in which Figure 1 is an elevational view of a direct-trip 25device embodying my invention.

Fig. 2 is a sectional view taken upon `the line II-H f Fig. 1. f Figs. 3and 4 are elevational views of a detail of the device shown in Figs. 1and 2. 30, Fig. 5 is a diagrammatic view of a magnetic circuit of myvimproved direct trip device.

Figs. 6, 7 and 8 are vector diagrams illustrating the operation of myimproved direct-trip device; and,

35. Figs. 9 and 10 are diagrammatic views of circuit breaker apparatusembodying my invention. In accordance with my invention, I utilize theprinciple of a pair of magnetic elements arranged to exert opposingforces upon a movable member, as disclosed in the United States patentto Edgar A. Hester, No. 1,948,711, issued Feb. 27, 1934, and assigned tothe Westinghouse Electric 8: Manufacturing Company. As explained in theabovementioned patent, the mechanical tripping" energy delivered by sucha device may be increased by causingvthe movable member to opcrate froma normally stable position through a mechanically unstable range to atripping position; However, in accordance with my inven- 50 tion, astraight line tripping characteristic may be produced, whereas thatofthe Hester device is necessarily a circle. 1 f

Referring to Fig. l, the direct trip device of my invention comprises amovable member I ar- 55.' ranged to be acted upon by opposing forcesproduced by an actuating element 2 and a restraining element 3. In thepreferred form of my invention, the movable member I is rotatablysupported upon a shaft 4 in suchl a manner thatv the elements 2 and 3normally exert opposing 5 moments or torques thereupon. It will beobvious, however, that there are numerous other mechanical arrangementssuitable for obtaining the balance of forces involved in my invention,and that the invention may be practiced with such other arrangements.

The actuating element 2 comprises a stationary magnetic structure 5consisting of a U-shaped. assembly of laminations arranged to form anopen magnetic circuit, the laminati'ons being sew cured together by anysuitable means such as bolts 5a. The magnetic 'structure 5 is fastenedto a suitable base plate 6 of non-magnetic materal, by any suitablefastening means (not shown), in a position to partially surround a bus20 bar 'I which carries the alternating-current to which the direct-tripdevice is to respond. The shaft I is mounted upon a pair of brackets 8,only one of which appears in Fig. l, seemed to the base plate 6 by meansof machine screws .8a. 25 The ends of the shaft 4 are 'threaded toreceive suitable fastening nuts la.

An armature 9 for the actuating element 2 is mounted in the air gap ofthe open magnetic structure 5, in such a manner as to close the 3@magnetic circuit upon rotation of .the member I in the counter-clockwisedirection.

The structure of the restraining element 3 is best shown 'in Fig. 2.Referring to Fig. 2, a laminated C-shaped pole-piece assembly I0 is se-35 cured by means of suitable non-magnetic spacers Il to a U-shapedassembly of laminations I2 in such a manner as to provide air gaps atpoints and y. The U-Shaped laminations of the assembly I2 are preferablyof the same size and 40 shape as those of the assembly 5, in order toprovide` similar magnetic characteristics, for a purpose as will behereinafter more fully explained.

The restraining element 3 is provided with an 45 armature I3, fastenedto a metallic block Il (see Fig. 2) which constitutes part of themovable member l. In the preferred form' of my invention, the armatureI3 is mounted upon a bolt I3a and is spaced from the block by means ofacompression spring I3b. A lock-nut I3c, threaded upon the bolt I3a,provides a means for adjusting the relative torques exerted on themovable member I by the actuating element 2 and the restraining element3. A pair of voltage windings Illa and 55 Ib are provided upon thepole-piece asembly Iii',

for a purpose which will hereinafter appear. The terminals of thewindings I 0a and Ib are brought out to a suitable terminal block Ic(see Fig. l).

The movable member i is preferably mechani-n cally balanced about theshaft 4 as an axis, and

' cally the entire magnetic circuit of the restraining comprises a pairof plates i5 and i6, separated by means of the block I4 and a lug 9a(see Fig. l) which constitutes part of the armature 9. Suitable machinescrews -i and a bolt it are provided for fastening the block iii and lug9a to the plates i5 and is. A tripping pin i9 is provided formechanically operating the toggle mechanism or latch ofA a circuitbreaker (not shown) in response to operation of ,the direct-tripdevice.A

The structure of the Q-shaped pole-piece as sembly i@ is best shown inFigs. 3 and 4. Referring to the latter gures, the laminations are ofsuch size and shape as to provide an eiiective air' gap z across theentire cross-section oi the Vmagnetic circuit. A pairjof lag loops Eiland 2l are set inthe pole faces of the assembly 8S, to

provide an out-of-phase component of iiux to 22 are located, and thelagloop 22 is designed' to absorb twice as much'power, during normaloperating conditions, as either lag loop 2@ or 2i. Referring to Fig. 5,which shows diagrammatielement 3, the magnetic structure i 2 isinductively interlinked with the equivalent single-turn circuit of thebus bar l, as indicated diagrammatically at la. However, because of theair gaps :c and y, the magnetic circuit divides into a leakage path 2d,an armature path 25 and a balancing path 25.

The purpose of this divided magnetic circuit is to make the mutualinductance of the voltage winding Ilia. and the main circuit 1a, equalto that of the potential winding IIib and-the main circuit 1a, so thatby connection of the windings Ilia and IIib in opposition, mutualinductance effects between the potential circuit and the main circuit'Ia may be eliminated.

Although the desired end may be accomplished in several ways, of suchlength that the total reluctance through the path 25 equals the totalreluctance through the Vpath 26. With `this relationship of reluctances, the windings Illa and Illb must have the same number of turns.As the power absorbed by the'lag loop 22 is equal vto that absorbed byboth lag loops 20 and 2l, the iiuxes producedin the paths 25 and 26 inresponse to given value of alternating vcurrent in the voltage windingsIlla equal in magnitude and phase position.

The effect of the ux which traverses the air- .gap path 24 is tointroduce series reactance in the buscircuit 1a. Such reactance is notordi-V narily objectionable, and in-network systems is, in fact,desirable.

The operation of the direct-trip device may be explained as follows,with reference to Fig. 5: The voltage windings I0a and IUb arepreferably connected in series and energized in accordance I prefertomake the air-gap z l .C may be rotated to other a main circuit voltagethrough a circuit which will be hereinafter pointed out. Assuming thenormal direction of iiux produced by the winding 50a to be as indicatedby the arrow-21, and the normal direction of uxproduced by the main gicircuit 'Ia to be as indicated by the arrows ib and 25, the uxes 2l and25 normally add, and the vector resultant of iiuxes .25 and 26 producesa restraining force on the armature I3.

It the phase position of the current'in the i@ main circuit ia becomessuch that the resultant of iiuxes 25 and 2i is reduced, the restrainingtorque produced by the element 3 may become less than the actuatingtorque of element 2, (Fig i) and the movable member i operates incounter- E@ clockwise direction. it will be noted that as the movablemember i leaves its normal'position, the restraining force produced bythe restraining element 3 becomes smailer and smaller because of the'increasing air `gap in the restraining element 3, and the actuatingforce produced by the ele ment i2 becomes greater and greater because ofthe reduction of its air gap. In this way, the force exerted by themovable member i rapidly increases as it leaves its normal position. 25The vector relationship of variables in the trip device is indicated inFig. 6, in which the eiiects or magnetic saturation are, forconvenience, not considered. Denoting the line voltage by E, the

voltage hun produced by the winding itla may be 33 represented by avector si having magnitude and phase position determined by theimpedance and phase angle of the potential circuit. An arbitrary valueof line current is indicated by the vector Such a vector produces aproportional nun' 2@ in 35 the actuating element 2, which forconvenience is shown to the 'saine scale. In the restraining element s,however, the iiux component Re corresponding to the current I, addsvectorially to the voltage nun 27, to produce a resultant ux 2d.

Assuming that the' lock-nut -I3c (shown in Fig. l.)v is adjusted so thatthe torque produced by the actuating element 2 Aexactly equals thetorque produced by the restraining element for a given value oi linecurrent, the magnitudes or actuating 35 and restraining forces areproportional to the nur.

vectors 28 and 29, respectively. As long asthe 'resultant vector 2Sremains greater in scaiar.

value than the vector 28, the restraining force exceeds the actuatingforce and the device does not operate.

However, if the resultant vector 29 attains a value suchl as'29',terminating on a perpendicular bisector B of the voltage ilux vector 2l,the aotuating force exactly equals the restraining force, as may be seenfrom the geometry oi' the arrangement. To produce this condition, thecorre sponding current vector must terminate on a line C parallel toline B. 'I'he line C accordingly represents the critical trippingcondition or tripping characteristic oi the direct-trip device. For any'current vector which terminates in the shaded area belowvthecharacteristic C, the device operates to trip open the associatedcircuit breaker.

Referring to Fig. 7,-" the tripping characteristic positions such as Cx,by changing the impedance phase angle of the potential circuitthroughthe lcoils Ila and IIIb, as by adding impedances of various types, as iswell understood in the relay art. Y By changing the adjustment of thelock-nut. I 3c, the straight-line tripping characteristic C may beconverted' into circular characteristics such as D or D1.

. Returning to Figs. 14andf2, as the magnetic 75 ilar banks forsupplying power equal. magnetic saturation tends to reduce the excess ofYtorque produced by the predominant elementat high current values. Thishas the effect of straightening out the portions of the' tripping'circle which correspond to high current values. Referring to Fig. 8, thepower' direc- .tional characteristic of the trip device may be changedto the characteristic O for example, which results from the effect ofmagnetic saturation upon a tripping circle such as D of Fig. '1. Thecurve O of Fig. 8 is substantially a directional over-currentcharacteristic. That is. to produce a tripping operation, the currentmust be of at least a predetermined minimum value Io, and must have apredetermined phase relationship as compared to the voltage E. J

Referring toy Fig. 9 in detail, a transformer bank Il, which may be oneor a number of simnetwork 32, is connected between a feeder 33 andseries impedances 4|,

`3411 and 34e for the three phases.

ytransmitting the mechanical tripping 51a, 31h and 31e to the one sideof a protector circuit breaker I4. I have 1illustrated the primarywindings of the transformer bank 3i connected in delta to the feeder '33and the secondary windings connected in star with neutral grounded. butit will be understood that my invention may The circuit breaker 34ispreferably of spe-` cialized construction having individual poles 34a,The poles 34a, 34h and 34c'are provided with separate springs 35a, 35hand 35e effective to operate the corresponding pole to fully openposition whenever it is moved past dead center. A mechanical lostmotionconnection 36 is provided for tripping open the two remaining poles,when any of the poles 34a, 34h or 34o has been moved beyond its deadcenter position. In this way, the trippingV of all the poles is broughtabout when any pole is tripped, although the initial latch load to tripthe entire breaker corresponds to that of. a single pole only. Thecircuit breakeri is' provided with a closing solenoid 38, operable toclose all the poles 34a, 54h and 34o as a unit.

Individual direct trip devices 31a, 31h and 31o, of the type describedabove, are provided for initiating the tripping of the individual polesin respense to a reverse power condition, or vector product of currentand voltage, above a predetermined value in the corresponding phase. Aset of lost motion trip rods 39 are provided for impulses of the directtrip devices corresponding poles 34a, 54h and 34e. n

The direct trip devices 31a, Ilb and 31o are provided with the pairs ofpotential windings i0a and/|01) describedabove in connection with Figs.1 and 2. However, for simplicity, the pairs of windings 10a and l0 arerrepresented together as the single winding 40 in Fig. 9. The windings 40are connected' in delta circuits which include and preferably also,saturable shunt reactors 42. The saturable ref actors 42 have the usualattened volt-ampere so that the actuating and restraining torques for agiven value of line current are not to a distribution be practiced withother connections known in the art. The circuit breakcharacteristic, andtend to carry a disproportionately large share of the current throughthe series impedance 4I at high voltages. In this way, a great reductionof voltage applied to the windings 40 is prevented in the event of lowline voltage during fault conditions. At the same time adequate voltageenergy is obtained at low line voltages without excessive heating of thepotential coils during normal voltage conditions.

To obtain the desired characteristics the re-- actors 42 are designed tosaturate at a voltage considerably below normal line voltage, such as ofnormal;

The closing solenoid 38 is connected in a closing circuit which includesa set of rectifiers 43, preferably of the dry or copper oxide type, andfront contact members of a voltage responsive relay 44. The voltageresponsive relay 44 is connected to the output terminals of aphase-sequence filter 45, preferably of the type described 20 Thephase-sequence filter 45 comprises an t0` auto-transformer 45a, having atap to provide a voltage less than half of the total voltage impressedon the auto-transformer, for example, a 40%V tap, and an impedanceconsisting of a reactor 45b anda resistor 45e having a combined 55lagging phase angle 'of 60. Assuming that the phase rotation of thesecondary voltages of the transformerbank 3| is as indicated by thesubscripts a, b, and c of the network conductorsua,

32h and J2e, the coil of the lvoltage responsive relay 44 is subject toa voltage equal to the vector sum of 40% of the voltage between the bphase transformer secondary terminal and thea phase transformersecondary terminal. and 40% of the voltage between the b phasetransformer secondary terminal and the c phase network conductor 32o,but lagging the latter voltage by 60. As explained in the abovementioned patent of B. E. Lenehan, the translating device correspondingto the voltage relay 44 is energized in accordance with a positivesymmetrical component of the polyphase voltage applied to the terminalsof the filter 45 under similar conditions.

,other net-work protectors supplied from the feeder and the opening of-the feeder circuit breaker (not shown). The lock-out relay 4B isdesigned to drop out at a low voltage such as 10% of normal line voltageand toreclose at a considerably higher voltage such as of Inormal linevoltage. I

A transfer relay 41A is provided for transferring the c-phase connectionof the l,phase sequence filter 45 fnom the network side of the protectorto the transformer secondary Iside whenthe network 32 is deenergized.

The operation of the apparatus shown in Fig. 9 may be set forth asfollows: The various relays .and switches are shown ln the positionswhich they assume when the network 32 and the' feeder work 32.

If a fault occurs on the network 32, the direction of power ow remainsnormal, and the fault is burned o in the usual manner.

It a fault occurs on'the feeder 33, the direction of power ilow reversesin one or more phase conductors, and one or more of the direct tripdevices 3'la, 31h or 31o operate toropen the corresponding poles 34a,34h or 34e-of the network circuit breaker 34. Because of the lost motionprovided in the trip rods 39, the direct trip device 37a, 31o or 31ewhich operates is permitted an initial movement before the trippingimpulse is transmitted to the corresponding pole of the circuit breaker34. The tripping force is, accordingly, greatly increased above thatwhich would be available if the direct-trip deviceA acted upon thecircuit breaker pole from its normal position. As soon as any of theindividual poles 34a., 34h or 34e is moved beyond its dead centerposition, the

corresponding spring 35a, 35h or 33e completes its opening operation,and the lost motion device 36 operates to trip out the two remainingpoles of the circuit breaker 34.

When the feeder 33 has been completely deenergized by the opening of allnetwork protectors supplied therefrom and by the opening of the feederbreaker (not shown) the lock-out relay 46 drops out to connect thevoltage responsive relay 34 to the phase sequencelter 45. Assuming thatthe network 32 remains energized, the transfer relay 41 remains closed,and the phase sequence lter 45 is energized in accordance with thepolyphase system of voltages consisting of two phases of transformersecondary voltage and one phase of networkvoltage. When the positivesymmetrical components of this system of polyphase voltages exceed a.predetermined value, such as"% of normal, the voltage responsive relay44 closes to complete an energizing circuit for the closing solenoid 38of the circuit breaker 34. The circuit breaker 34, accordingly,recloses. If, however, upon the opening of the circuit i breaker 34, thedistribution network 32 is deenergized, the transfer relay 41 drops outand the phase sequence illter 45 is energized in accordance with thepolyphase secondary voltage of the transformer bank 3|. In this way, itis possible for the network circuit breaker 34 to bereclosed when thenetwork 32 is deenergized, if the transformer secondary phase vvoltagesare of substantially normal value and correct phase sequence. Although Ihave described my invention as applied to a specialized circuit breakerconstruc-l tion having individual pole tripping, the invention isequally applicable to single phase circuit breakers or to polyphasecircuit breakers in which the poles are operated as a unit.

Fig. 10 shows diagrammatically an application of my invention to apolyphase circuit breaker 50, with individual direct trip devices 31 forseparate phases connected mechanically together as a unit. A lostmotion' connection 48 is provided between the direct trip devices 3l andthe latch soa/of the nrt-uitA breaker. with this arrangement the directtrip devices 31 totalize the power of all phases, and operation occurswhen thepolyphase reverse power iiowexceeds a predetermined value.

I do not intend that the present invention shall' be restricted to thespeciiic details, arrangement of parts, or circuit connections hereinset forth, as various modifications thereof may be eiiected withoutdeparting fron the'spirit and scope of aoaaaai my invention. I desire,therefore, that only such limitations shall be imposed as are indicatedin the `appended claims.

I claim as my invention:

1. ,In an alternating-current direct-trip device, 5 a movable trippingmember operable to a tripping position, an electromagnetic actuatingelement energized solely in accordance with a current condition formoving said member to said position, anda second electromagnetic elementenergized 10 in accordance with a voltage condition and a currentcondition for preventing movement of said member to said position exceptunder predetermined conditions of current and voltage.

2. In an alternating-current direct-trip device, 15 aymovable trippingmember operable from a normal position to a tripping position. anelectromagneticactuating element energized solely in accordance with acurrent condidtion for moving said member from said normal position tosaid z 0 tripping position, said actuating element being eiiective todevelop increasing force with increasing displacement of said memberfrom said normal position, and a second electromagnetic elementenergized in accordance with a voltage condition and a currentcondidtion for preventing movement of said member from said normalposition except under predetermined conditions of current and voltage.

3. In an altemating-current direct-trip .de- 30 vice, a movable trippingmember operable from a normal position to a tripping position, anelectromagnetic actuating element energized solely in accordance with acurrent condition i'orl moving said member from' said normal 'positionto $4 said tripping position, and an electromagnetic restraining elementenergized in accordance with a voltage condition and a current conditionfor exerting a restrainingNrce on saidl member to prevent movementthereof from said normal position except under predetermined condidtionsof current and voltage, said restraining element being eiective todevelop decreasing restraining force with increasing displacement ofsaid member from said normal position. t5

4. In an alternating-current device responsive to a vector product of avoltage condition and a second electrical condition, a A voltagewinding, a. series impedance, a shunt impedance, a voltage energizingcircuit for said winding including said winding and said shunt impedancein parallel relationship and said series impedance in seriesrelationship, said impedances having volt-ampere characteristics sorelated as to cause the percentage variation oi' voltage applied to saidwinding 55 to be less than the percentage variation of voltage appliedto said lenergizing circuit, for a change of the latter voltage betweenpredetermined limits.

5.'In an alternating-current device responsive 60 to a vector product ofa voltage condition and a second electrical condition, a voltagewinding, a series impedance, shunt impedance means having a flattenedvolt-ampere characteristic within predetermined-limits of appliedvoltage, and a 65 voltage energizing circuit for said winding includingsaid winding and said -shunt impedance in parallel relationship and saidseries impedances in series relationship.

6. In an alternating-current device responsive 70 to a vector product-ofa voltage condidtion and -a second electrical/condition; a voltagewinding, a

. condition,

allel relationship and 'said series impedance in series relationship.

7. In an alternating-current direct-trip device, a movable trippingmember, an actuating element and a restraining element arranged to exertopposing forces upon said member, each oi.' said elements having amagnetic portion responsive to a common electrical condition, saidportions being designed to have similar magnetization characteristics,and means for inductively energizing said portions to the same fluxdensity for each value Voi said condition to thereby substantiallybalance the eiects of magnetic saturation in said device. i

8. In an alternating-current direct-trip device, a movable trippingmember, an. actuating element and a restraining element arranged toexert opposing forces upon said member, each of said elements having amagnetic portion responsive to a common electrical condition, saidportions having figuration in the plane of magnetic flow, and means forinductively energizing said portions to a common flux density ior eachvalue of said to thereby substantially balance the effects of magneticsaturation in said device.

9. In an alternating-current direct-trip device, a movable trippingmember, an actuating element and a restraining element arranged to exertopposing forces upon said member, each oi said elements having anassembly of laminations responsive to a common electrical condition,said laminations being similar in size and design for both of saidelements, and means for inductively energizing said laminations to acommon flux density for each value of said condition, to therebysubstantially balance the effects of magnetic saturation in said device.

10. In an alternating-current direct-trip device, a magnetic structurearranged to provide a magnetic circuit having a pair of parallelbranches and a common portion, a ilrst means for inductively energizingsaid common portion in accordance with a iirst electrical condition, asecond means for inductively energizing one of said parallel branches inaccordance with a second electrical condition, a third means foroppositely energizing the remaining one of said parallel branches inaccordance with said second electrical condition, and a commonenergizing circuit for said second and third means,

the mutual reactance of said rlrst and second` means being equal to themutual reactance oi said iirst and third means, whereby inductiveinterference between sa'd first means and said common energizing circuitis eliminated.

11. In an alternating-current direct-trip device, magnetic structurearranged to provide a magnetic circuit having a pair of parallel thesame area and similar con` branches and a common portion, means forinductively energizing said common portion in accordance with a currentcondition, a pair oi windings for inductively energizing said parallelbranches in opposite directions in accordance with a voltage condition,and a common energizing circuit for said windings, the mutual reactancesof said windings to said means being equal, whereby inductiveinterierence between said means and said common energizing circuit iseliminated.

12. In an alternating-current direct-trip device, magnetic structurearranged to provide a magnetic circuit having a pair of parallelbranches of equal reluctance and a common portion, a first means forinductively energizing said common portion in accordance with a iirstelectrical condition, a second means for inductively energizing one ofsaid parallel branches in `accordance with a second electricalcondition, a third means ior oppositely energizing the remaining one ofsaid parallel branches in accordance with said second electricalcondition, and a common energizing circuit for said second and thirdmeans, said second and third means being of equal number of effectiveturns whereby inductive interference between said first meansV circuitis avoided.

14. In an alternating-current"direct-trip device, a magnetic structurearranged to provide a first branch having a movable armature therein, asecond branch in parallel to said first branch, and a common portion inseries with both of said branches, means for balancing a magneticcondition ci corresponding condition of said second branch comprisingmeans for inductively energizing said branches in opposite directions, afirst lag loop means interlinked with part of said first branch adjacentsaid armature to prevent chattering oi said armature, and a second lagloop means interlinked with a corresponding part of said second branchto balance the eiect of said first lag loop means.

said first branch with aA

